Vahid Morshedi

This study aims to investigate the effects of different salinities without adaptation on blood electrolytes and the structure of gill and kidney tissues in Asian sea bass (Lates calcarifer). A number of 180 Asian sea bass juveniles with an average initial weight of 34±1g were randomly selected and distributed in 4 treatments each with 3 replications including treatment 1 to 4 (salinity of 0, 15, 35 and 50g/L). The sampling of fish was done at 6, 24, 72 and 120 hours. No mortalities were observed during the experimental period. The results of the present study showed that different salinities caused significantly changes in the amount of osmolality and sodium, potassium and chlorine ions in the blood of Asian sea bass in different hours of the experiment (P<0/05). Lesions such as epithelial necrosis and adhesion of lamellae were observed in the gill tissue of the 0, 15 and 35 g/L salinity groups than the 50g/L salinity group. Also, in the kidney tissue of the 0, 15 and 35g/L salinity groups, lesions such as an increase in the concentration of melano-macrophages, an enlargement of Bowman's capsule, an increase in the space in the center of the glomerulus, and necrotic cells in the hematopoietic tissue were observed compared to the 50g/L salinity group. The highest level of gill and kidney tissue damage in this fish belonged to the 0g/L salinity group and the lowest level belonged to the 50g/L salinity group. The results showed that different salinities without adaptation can change blood electrolytes and the structure of gill and kidney tissues in Asian sea bass.